LeetCode 2 Add Two Numbers，leetcodenumbers

LeetCode 2 Add Two Numbers，leetcodenumbers

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

# Definition for singly-linked list.# class ListNode#     attr_accessor :val, :next#     def initialize(val)#         @val = val#         @next = nil#     end# end# @param {ListNode} l1# @param {ListNode} l2# @return {ListNode}def add_two_numbers(l1, l2)    return l1 if l2.nil?    return l2 if l1.nil?    s1 = Array.new    s2 = Array.new    n = Array.new    while l1        s1.unshift(l1.val)        l1 = l1.next    end    while l2        s2.unshift(l2.val)        l2 = l2.next    end    x = s1.join.to_i+s2.join.to_i    n = x.to_s.chars.map(&:to_i)        ans = ListNode.new(0)    d = ans    l = n.length()    l.times do        d.next = ListNode.new(n.pop)        d = d.next    end    ans.nextend